1. Field of the Invention
The present invention relates to a write once optical disc and a method and apparatus for recovering disc management information from the write once optical disc.
2. Background of the Related Art
Optical discs are used widely as optical media for recording large sized data. Among the optical discs, recently a new high-definition digital video disc (HD-DVD) type of recording media, such as a Blu-ray disc, is under development. High definition video data and high definition audio data can be written and stored on such a Blu-ray disc for a long time. The Blu-ray disc, the next generation HD-DVD technology, can store much more data than the currently available DVDs.
Generally, the Blu-ray disc has a 1.2 mm thickness and a 12 cm diameter with a 0.1 mm thick optical transmission layer accessible with a bluish violet laser having a 405 nm wavelength, which is much finer than the currently available DVD that uses a red laser having a 650 nm wavelength.
Various draft standards for the Blu-ray disc are under preparation. In this regard, various draft standards for a Blu-ray disc write once (BD-WO) are under preparation in succession to a Blu-ray disc re-writable (BD-RE). A BD-WO is a write once Blu-ray optical disc that allows only one time recording on its area, whereas a BD-RE is a rewritable Blu-ray optical disc that allows recording, erasing and repeated recording of its area.
FIG. 1 illustrates a structure of a recording area of a BD-RE, schematically. The Blu-ray disc in FIG. 1 has one recording layer provided with, starting from an inner circumference of the disc, a lead-in area, a data area, a lead-out area. The data area has an inner spare area (ISA0) and an outer spare area (OSA0) respectively in the inner and outer circumferential parts of the data area, and a user area in the middle part of the data area for the user's data writing/recording.
If a defective area in the data area of the BD-RE is detected in the middle of data writing, a replacement writing operation is carried out in which the data in the defective area is transferred to the spare area. Then, as management information on the defective area, information on the positions and the like of the defective area and on the used replacement area is written in defect management areas (DMA1, DMA2, DMA3, and DMA4) of the lead-in/out areas, for management of defects.
However, since the writing on a particular area is possible only once in the write once optical disc, it is important to manage well position information indicating whether or not an area has a data written thereon, position information indicating the location of the disc area to which data can be written, defective area information indicating the location of defective areas, and the like. In the consolidated standards for write once optical discs such as BD-WOs under development, establishment of consolidated standards would be needed for methods of providing defect management information and recovering the defect management information in case the defect management information is damaged or has not yet been written. If data are written on a disc without recovering the lost disc management information, many problems would arise such as writing data based on incorrect prior management information and obtaining an incorrect position of the recordable area on the disc.